Incorporating biophilic design principles in landscape architecture is essential if our cities are to become more climate resilient. Here, Richard Sabin, Managing Director of Biotecture, looks at why that and other benefits make living walls the stand-out choice for overcladding projects.
Over the last few years, the UK has faced a number of pressing urban challenges including poor air quality, loss of biodiversity and urban heat island effect. There is a growing understanding that living walls provide an effective way to help tackle these issues, particularly when space is at a premium.
That brings us appropriately enough to the questions that we are commonly asked by architects and designers about adding living walls to existing buildings.
Can living walls be fitted as a rainscreen cladding system on an existing building?
Yes, living wall systems are available that are designed and validated to ‘work’ as the rainscreen cladding element of buildings, whether fitted to a new or existing building. That makes a living wall system integral to the building design and in terms of value should be considered against other cladding systems rather than being seen as an additional cost.
They comprise a supporting framework that is anchored back to the structure, along with CP board, waterproof membrane, ventilated cavity and vegetative panels.
The total overall outward projection of a living wall from the structure can be as little as 80mm, which is again comparable with other rainscreen systems.
Do living walls impose weight loadings on existing facades?
As with any rainscreen cladding system that is used to overclad an existing building, it is necessary to carry out a structural survey to verify that the structure can withstand additional loading.
A structural survey will inform you of the most appropriate living wall system to use. Where the survey identifies that the facade is capable of accepting additional weight loading, it is possible to use a living wall product, such as BioPanel, which is similar to any rainscreen cladding system. If the existing masonry facade won’t accept additional weight loading, we guide specifiers as to the best way forward.
Where else can I specify living walls?
Living wall systems can be used in a wide range of other locations, such as low-level walls, balconies, boundary walls, perimeter fences for industrial plants, site hoardings, railings, roof gardens or terraces.
How do living walls help us tackle the climate emergency?
Living walls help address the climate emergency in a number of ways. They help mitigate the heat island effect – proliferation of concrete, steel and tarmac in our cities absorb huge amounts of heat, creating their own microclimate. These elevated temperatures drive the need for energy-intensive air conditioning and cooling systems in what becomes a vicious circle. Living walls tackle this by creating building bio membranes, which involves choosing plant species that filter out sunlight, keeping the underlying surface of the building cooler and so minimising solar gain. That means that the inside of the building is cooler in summer and, with the effect reversed, warmer in winter. This can reduce the amount of heating ventilation and air conditioning that is needed.
Living walls also increase biodiversity at a time of alarming decline in pollinators and other species. Growing plants also result in the sequestration of carbon, whilst photosynthesis captures carbon dioxide from the atmosphere and converts it into oxygen.
What other benefits do living walls offer?
Living walls help us address the climate emergency as well as bringing specific benefits to the people living and working in cities. Principally, they bring biodiversity to our cities and that is important because it supports pollinators, ensures natural sustainability and creates healthier systems. They also help to mitigate the effects of air pollution whilst enriching our urban spaces, which has been shown to have a positive impact on mental wellbeing and allowing people to reconnect with nature.
Being close to nature is good for us and has been shown to reduce heart rate and blood pressure as well as improving mental health, according to the British Heart Foundation.
Living walls also create a building bio membrane, which filters out sunlight, keeping the underlying surface of the building cooler and so minimising solar gain in summer. The effect is reversed in winter, so keeping the building warmer.
Do living walls help with the planning process?
The new Environment Bill, which passed into law in November, will require new developments to protect and improve the biodiversity of the plot by at least 10%. Living walls are a space-efficient method of introducing Biodiversity Net Gain and so can contribute to the planning process.
How do I ensure my living wall continues to flourish?
Living walls have a service life equivalent to many other cladding systems. That means, with a regular maintenance programme in place, they will flourish indefinitely.
The technology we use to maintain living walls has improved beyond recognition in recent years. For example, we use remote sensing irrigation systems, and water is delivered directly to the root zone. This enables precision watering that uses a quarter of the water required on equivalent horizontal landscapes.
Grodan is the growing medium we use for our hydroponic living walls, a 100% natural material that is based on spun rock. It acts as a water-retentive sponge and results in healthier and longer-lasting plants. It is ideally suited to living walls because it allows plants to be grown in relatively thin bases, minimising outward projection from the structure to as little as 80mm.
Three of our living walls have just celebrated their 10th anniversary, looking as good as the day they were installed, and continuing to flourish.
Climate change and demand from urban planners for greater biodiversity means that more architects are incorporating living walls into their designs. That bodes well for the future because plants should be an integral element of urban landscapes not least because they improve welfare of people and tackle the challenges of our time.
We all want our urban spaces to be places where people can thrive and so it is a win-win when we can say that living walls do this whilst delivering these important benefits. The move to net zero, demand from developers that see the long-term value in living walls and the Environment Bill will continue to drive the agenda. We can see there are challenges but also with it, immense opportunities to revolutionise the design of our urban spaces.